Police in Hong Kong arrested more than 50 people Wednesday for apparent violations of a China-imposed "national security law"- the latest in a series of crackdowns that have seen several prominent pro-democracy Catholics arrested and charged on the island.

Among those arrested Jan. 6 are a number of politicians and organizers who took part in unofficial "primaries" to choose opposition candidates for the next elections in Hong Kong. The territory was slated to hold parliamentary elections during September 2020, but officials postponed them, citing dangers posed by the coronavirus pandemic.

A Chinese foreign ministry spokeswoman told the BBC that the arrests were necessary to stop "external forces and individuals [colluding] to undermine China's stability and security."

Several of those arrested this week were opposition candidates hoping to win election to the territory's parliament, or Legislative Council. The unofficial primaries were held during July 2020 with some 600,000 Hong Kongers participating.

The UK-based group Hong Kong Watch called the arrests a "purge of pretty much the entire pro-democracy camp." Half the seats on the Legislative Council are already controlled by those with vested interests in the Chinese Communist Party, the group reported.

Also arrested was an American citizen, lawyer John Clancey, the first known foreigner to be arrested under the national security law, UCA News reported. Clancey was the treasurer for the organization that coordinated the democratic primaries, HKW reported.

Benny Tai, a Christian pro-democracy organizer who also helped with primaries, also faced arrest. Police also reportedly raided the home of Joshua Wong, a student activist who was previously arrested and has already been charged.

Hong Kong's National Security Law went into effect July 1, 2020, imposed directly by Beijing. It has been criticized as being overly broad on its definitions of terrorism, sedition, and foriegn collusion.

Under the law, a person who is convicted of the aforementioned crimes will receive a minimum of 10 years in prison, with the possibility of a life sentence.

American politicians including the prospective secretary of state under the incoming Biden administration have condemned the police's actions. The US Consulate in Hong Kong would not comment on the arrests, according to CNN.

Hong Kong is a "special administrative region" of China, meaning it has its own government but remains under Chinese control. It was a British colony until 1997, when it was returned to China under a "one country, two systems" principle, which allowed for its own legislature and economic system.

Hong Kong's openness to the outside world, and transparency in business and banking regulation, in contrast to mainland China, has made it a center of global business, banking, and finance.

Millions of citizens of Hong Kong, including many Catholics, have in recent years participated in large-scale pro-democracy protests in Hong Kong, which came to a head during summer 2019.

At that time, the protestors successfully rebuffed the Hong Kong legislature's efforts last year to pass a bill that would have allowed mainland China to extradite alleged criminals from Hong Kong.

However, with the passage of the new security laws, the Chinese government seized more power to suppress the protests in Hong Kong, which it sees as a direct challenge to its power.

Similar security rules have been proposed before; in 2003, the communist government attempted to use Hong Kong's own legislative and executive councils to pass the anti-sedition measures, but massive protests led lawmakers to abandon the proposal.

(Story continues below)

Cardinal John Tong Hon, apostolic administrator of Hong Kong, previously downplayed religious freedom concerns about the law.

In June 2020, Cardinal Tong told a diocesan publication that he "personally believe that the National Security Law will have no effect on religious freedom, because Article 32 of the Basic Law guarantees that we have freedom of religion, and we can also openly preach and hold religious ceremonies, and participate in religious activities."

In recent months, the Diocese of Hong Kong has issued directives to Catholic schools on "fostering the correct values on national identity" and respecting Chinese national symbols including the flag and national anthem. It has also blocked a Catholic pro-democracy ad campaign and prayer that was set to run in local newspapers.

The last large crackdown in Hong Kong occurred in August 2020, when several prominent democracy activists were arrested and charged, including Agnes Chow, a 23-year-old Catholic democracy activist. Chow has been outspoken in her support for civil rights in the former British colony.

In November, three of the pro-democracy activists, including Joshua Wong and Chow, pled guilty on charges related to their roles in an "illegal assembly" in 2019. The next month, they were each sentenced to months in prison, with the possibility that they will face further charges.

Also among those arrested in August was Jimmy Lai, a Catholic media executive who has supported the Hong Kong pro-democracy movement for the past 30 years. A band of nearly 200 police officers arrested Lai Aug. 10, along with at least nine others connected to Apple Daily, the newspaper Lai founded in 1995.

Following those arrests, Cardinal Tong wrote to local clergy, warning them against mentioning politics in their homilies, according to Apple Daily.

Lai was free on bail for a time, but in early December was charged with foreign collusion. If convicted, he could receive a life sentence. Lai was also charged in early December 2020 with breaching the terms of a lease for his company, Next Digital Media.

After another brief period out on bail, Lai was ordered back to jail on Dec. 31, where he is set to remain until a hearing in February. His trial is expected to begin in April.

Cardinal Joseph Zen Ze-kiun, bishop emeritus of Hong Kong, has warned that Lai's arrest shows a rise in "political intimidation" against journalists in Hong Kong, part of a systematic erosion of basic freedoms, including religious freedom, by the Chinese government in recent months.

Zen has been an outspoken critic of the Holy See's accord with the Chinese government, first agreed in 2018 and recently renewed for another two years. Zen has explained to CNA that, in past decades, the Church has had a key role to play in promoting the values of human dignity and freedom in Hong Kong – a role that is now being steadily eroded.